Xrays, stall rest

Cupid was x-rayed on Tuesday.  The good news was no fracture or bone cyst.  The bad news is we still don't know why he is lame!  The vet still believes the problem is coming from the stifle.  The recommendation was to put him on stall rest for about 10 days and see where he's at and decide if ultrasounds are needed.  Cupid is a pretty good patient, he doesn't mind being in the stall but then is a little pushy when I bring him out he sometimes doesn't want to stand still.  I've been going out in the morning and after work to let him out to graze and very minimal walk.  Unfortunately it gets pretty warm in the stall during the day.  I need to get him a salt lick, and maybe a stall toy.